This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the presently described embodiments. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present embodiments. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
In order to meet consumer and industrial demand for natural resources, companies often invest significant amounts of time and money in searching for and extracting oil, natural gas, and other subterranean resources from the earth. Particularly, once a desired subterranean resource is discovered, drilling and production systems are often employed to access and extract the resource. These systems may be located onshore or offshore depending on the location of a desired resource. Such systems generally include a wellhead assembly through which resources are extracted.
In the case of an offshore system, such a wellhead assembly may include one or more subsea components that control drilling and/or extraction operations. For instance, such components may include one or more production trees (often referred to as “Christmas trees”), control modules, a blowout preventer system, and various casings, valves, fluid conduits, and the like, that generally facilitate the extraction of resources from a well for transport to the surface. Some of these components may include sub-components or devices that are configured for linear movement. For example, a blowout preventer system may include multiple blowout preventers assembled in a stack-like arrangement. Each of these blowout preventers may include one or more pistons that are configured to move in a linear direction when actuated. For instance, in the case of a ram-type blowout preventer, opposing pistons may be translated horizontally toward each other (e.g., via hydraulic actuation) to drive a corresponding pair of opposing rams toward the center of a wellbore. Other examples of linearly actuated devices that may be present in subsea equipment include various types of pressure or flow control devices, such as valves, connectors, and so forth.
Position monitoring (also referred to as ranging) with respect to such linear moving components has been an ongoing challenge for the industry, particularly with respect to devices that are deployed in subsea environments. Without an adequate position monitoring system, it is difficult for operators to assess the position of a linearly actuated component or how far the component has translated in response to an actuation event. Moreover, due to the harsh environments in which subsea equipment is often operated, the ability to monitor the condition of the subsea equipment is also useful. Having a reliable position monitoring system in place may provide for improved condition monitoring of subsea equipment. For example, position monitoring may be useful for determining whether or not a particular component exhibits an expected behavior in response to an actuation control input. In the absence of reliable position information, condition monitoring metrics may rely more heavily on the relationship between time parameters and actuation parameters, which may be insufficient to accurately delineate normalized condition status.
Existing solutions for position monitoring have included the use of electromechanical position sensing devices in conjunction with linearly actuated components. One example of an electromechanical position sensing device is a linear variable differential transformer (LVDT). However, the use of electromechanical devices in position monitoring is not without drawbacks. For instance, electromechanical devices, such as LVDTs, may be subject to a common-mode failure, as they are subject to a level of mechanical degradation similar to the component being monitored. Further, the incorporation of electromechanical position sensing devices into existing subsea equipment may require that existing equipment be redesigned and modified to accommodate the electromechanical position sensing devices and associated components, which may be not only be costly and time consuming, but oftentimes impractical.